Electrical transport properties and conduction mechanisms of semiconducting iron bismuth glasses

Abstract

DCelectrical conductivity measurements were carried out on iron bismuth glasses with the nominal composition (100–x)Bi2O3–x Fe2O3(where x=15, 25, 35and 45mol%) in an attempt to understand the nature of the conduction mechanism governing the DC electrical conductivity and the effect of addition of Fe2O3 on electrical properties in these glasses. The investigated glasses were prepared by a normal melt quenching technique. X-ray diffraction (XRD) patterns confirmed the amorphous nature of the present glasses. DC conductivity measurements showed an enhancement in conductivity by increasing Fe2O3 concentration. The change in activation energy of DC conductivity with temperature reveals the change in conduction mode from small polaron hopping (SPH) at high temperatures (T>θD/2) to variable range hopping (VRH) at low temperatures (T<θD/2). The conductivity results were analyzed in terms of different theoretical models to determine the possible conduction mechanism. The analysis showed that the conductivity data are consistent with Mott's nearest-neighbor SPH model. However, both Mott VRH and Greaves VRH models are suitable to explain the data. Further, Schnakenberg's polaron hopping model is also consistent with the temperature dependence of the activation energy, but the different model parameters, for example, hopping energy and disorder energy determined from the best fits were found not to be in accordance with the prediction of the SPH model.